The Sky Is Falling

by Lester Del Rey

Hanson stared at them and around at the collection of bric-a-brac and machinery they had assembled for him. He opened his mouth, and his laughter was a mockery of their hopes and of himself.

"Dave Hanson, world saver! You got the right name but the wrong man, Sather Karf," he said bitterly. He'd been a pretender long enough, and what punitive action they took now didn't seem to matter. "You wanted my uncle, David Arnold Hanson. But because his friends called him Dave and cut that name on his monument, and because I was christened by the name you called, you got me instead. He'd have been helpless here, probably, but with me you have no chance. I couldn't even build a doghouse. I wasn't even a construction engineer. Just a computer operator and repairman."

He regretted ruining their hopes, almost as he said it. But he could see no change on the old Sather's face. It seemed to stiffen slightly and become more thoughtful, but there was no disappointment.

"My grandson Bork told me all that," he said. "Yet your name was on the monument, and we drew you back by its use. Our ancient prophecy declared that we should find omnipotence carved on stone in a pool of water, as we found your name. Therefore, by the laws of rational magic, it is you to whom nothing is impossible. We may have mistaken the direction of your talent, but nonetheless it is you who must fix the sky. What form of wonder is a computer?"

Dave shook his head at the old man's monomania. "Just a tool. It's a little hard to explain, and it couldn't help."

"Humor my curiosity, then. What is a computer, Dave Hanson?"

Nema's hand rested on Hanson's arm pleadingly, and he shrugged. He groped about for some answer that could be phrased in their language, letting his mind flicker from the modern electronic gadgets back to the old-time tide predicter.

"An analogue computer is a machine that ... that sets up conditions mathematically similar to the conditions in some problem and then lets all the operations proceed while it draws a graph—a prediction—of how the real conditions would turn out. If the tides change with the position of some heavenly body, then we can build cams that have shapes like the effect of the moon's orbit, and gear them together in the right order. If there are many factors, we have a cam for each factor, shaped like the periodic rise and fall of that factor. They're all geared to let the various factors operate at the proper relative rate. With such a machine, we can run off a graph of the tides for years ahead. Oh, hell—it's a lot more complicated than that, but it takes the basic facts and draws a picture of the results. We use electronic ones now, but the results are the same."

"I understand," Sather Karf said. Dave doubted it, but he was happy to be saved from struggling with a more detailed explanation. And maybe the old man did understand some of it. He was no fool in his own subject, certainly. Sather Karf pondered for a moment, and then nodded with apparent satisfaction. "Your world was more advanced in understanding than I had thought. This computer is a fine scientific instrument, obeying natural law well. We have applied the same methods, though less elaborately. But the basic magical principle of similarity is the foundation of true science."

Dave started to protest, and then stopped, frowning. In a way, what the other had said was true. Maybe there was some relation between science and magic, after all; there might even be a meeting ground between the laws of the two worlds he knew. Computers set up similar conditions, with the idea that the results would apply to the original. Magic used some symbolic part of a thing in manipulations that were to be effective for the real thing. The essential difference was that science was predictive and magic was effective—though the end results were often the same. On Dave's world, the cardinal rule of logic was that the symbol was not the thing—and work done on symbols had to be translated by hard work into reality. Maybe things were really more logical here where the symbol was the thing, and all the steps in between thought and result were saved.